From: Leon Romanovsky <[email protected]> Exporters keep the &struct p2pdma_provider backing a buffer in their own private data. An importer cannot reach it, so it has no way to learn how its own peer-to-peer traffic would be routed before it programs its hardware.
Add an optional @p2pdma_provider callback for an exporter to hand that provider out, and dma_buf_p2pdma_map_type() for an importer to ask by TLP class. Exporters keep the provider where it already lives, so this adds an operation rather than changing any existing signature or structure. Tested-by: Tushar Dave <[email protected]> Signed-off-by: Leon Romanovsky <[email protected]> --- drivers/dma-buf/dma-buf-mapping.c | 39 +++++++++++++++++++++++++++++++++++++++ include/linux/dma-buf-mapping.h | 3 +++ include/linux/dma-buf.h | 19 +++++++++++++++++++ 3 files changed, 61 insertions(+) diff --git a/drivers/dma-buf/dma-buf-mapping.c b/drivers/dma-buf/dma-buf-mapping.c index 794acff2546a..41702045f803 100644 --- a/drivers/dma-buf/dma-buf-mapping.c +++ b/drivers/dma-buf/dma-buf-mapping.c @@ -6,6 +6,45 @@ #include <linux/dma-buf-mapping.h> #include <linux/dma-resv.h> +/** + * dma_buf_p2pdma_map_type - How peer-to-peer traffic to a buffer is routed + * @attach: attachment of the importer that will issue the traffic + * @tlp_flags: &enum pci_p2pdma_tlp_flags describing the TLPs it will issue + * + * Reports how the PCIe fabric routes @tlp_flags traffic between the buffer + * behind @attach and the importer attached to it, so that an importer can + * choose the TLP attributes that earn it a direct route before it programs + * its hardware. + * + * The caller must hold the reservation lock. The provider is owned by the + * exporter's driver binding, and exporters revoke under that lock before + * letting an unbind proceed, so dropping it any earlier would leave this + * racing a teardown that frees the provider. + * + * Return: the mapping type for @tlp_flags traffic, or PCI_P2PDMA_MAP_NONE + * when the exporter names no &struct p2pdma_provider and nothing is known + * about the route. + */ +enum pci_p2pdma_map_type +dma_buf_p2pdma_map_type(struct dma_buf_attachment *attach, + unsigned int tlp_flags) +{ + struct dma_buf *dmabuf = attach->dmabuf; + struct p2pdma_provider *provider; + + dma_resv_assert_held(dmabuf->resv); + + if (!dmabuf->ops->p2pdma_provider) + return PCI_P2PDMA_MAP_NONE; + + provider = dmabuf->ops->p2pdma_provider(dmabuf); + if (!provider) + return PCI_P2PDMA_MAP_NONE; + + return pci_p2pdma_map_type_tlp(provider, attach->dev, tlp_flags); +} +EXPORT_SYMBOL_NS_GPL(dma_buf_p2pdma_map_type, "DMA_BUF"); + static struct scatterlist *fill_sg_entry(struct scatterlist *sgl, size_t length, dma_addr_t addr) { diff --git a/include/linux/dma-buf-mapping.h b/include/linux/dma-buf-mapping.h index 09bde3f748e4..37b3da10b17a 100644 --- a/include/linux/dma-buf-mapping.h +++ b/include/linux/dma-buf-mapping.h @@ -7,6 +7,9 @@ #define __DMA_BUF_MAPPING_H__ #include <linux/dma-buf.h> +enum pci_p2pdma_map_type +dma_buf_p2pdma_map_type(struct dma_buf_attachment *attach, + unsigned int tlp_flags); struct sg_table *dma_buf_phys_vec_to_sgt(struct dma_buf_attachment *attach, struct p2pdma_provider *provider, struct phys_vec *phys_vec, diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index d1203da56fc5..d56a48d41215 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -186,6 +186,25 @@ struct dma_buf_ops { * if the call would block. */ + /** + * @p2pdma_provider: + * + * Returns the &struct p2pdma_provider backing this buffer, so that an + * importer can ask how its peer-to-peer traffic would be routed before + * it programs its hardware. Importers reach this through + * dma_buf_p2pdma_map_type() rather than calling it directly. + * + * Exporters of MMIO memory that is reachable peer-to-peer should + * implement this. Called with the &dma_buf.resv reservation lock held, + * which is what lets an exporter refuse once it has revoked the buffer + * and started tearing the provider down. This callback is optional. + * + * Returns: + * + * The provider backing the buffer. + */ + struct p2pdma_provider *(*p2pdma_provider)(struct dma_buf *dmabuf); + /** * @release: * -- 2.55.0
